1. Field of the Invention
The present invention relates to a roll straightener for straightening a work.
2. Description of the Related Art
Heretofore, there has been known a roll straightener wherein plural pairs of rolls are arranged in upper and lower rows and a work is passed between upper and lower rolls so as to be straightened. There is a case where the work is passed without rotation and a case where it is passed with rotation. Straighteners are broadly classified into a zigzag type and an opposed type, depending on the layout of rolls.
First, a zigzag type roll straightener will be described with reference to FIG. 5. For example, the zigzag type roll straightener is provided with seven upper rolls 51, 52, 53, 54, 55, 56, 57 and seven lower rolls 61, 62, 63, 64, 65, 66, 67. Upper roll 51 and lower roll 61 are aligned vertically with each other at an inlet side where a work 10 such as a pipe is introduced. At an outlet side, three pairs of upper rolls 55, 56, 57 and lower rolls 65, 66, 67 are disposed so that each pair of rolls are aligned vertically with each other. The three upper rolls 55, 56 and 57 are set at the same height and, likewise, the three lower rolls 65, 66 and 67 are set at the same height. Second to fourth upper rolls 52, 53, 54 and lower rolls 62, 63, 64, which are close to the inlet side (the rolls located closest to the inlet side are assumed to be first rolls), are disposed in a zigzag fashion (the upper and lower rolls assume alternate positions). The second to fourth upper rolls 52, 53 and 54 are positioned a certain fraction of a millimeter below the other upper rolls 51, 55, 56 and 57. Likewise, the second to fourth lower rolls 62, 63 and 64 are positioned a certain fraction of a millimeter above the other lower rolls 61, 65, 66 and 67.
The work 10 is moved from between the inlet-side (first) upper roll 51 and lower roll 61 toward the outlet-side (seventh) upper roll 57 and lower roll 67. After passing the zigzag upper rolls 52, 53, 54 and lower rolls 62, 63, 64, the work passes three pair of respectively vertically aligned upper rolls 55, 56, 57 and lower rolls 65, 66, 67, whereby the work 10 is straightened. This zigzag type roll straightener is advantageous in that the roundness is good, but is markedly disadvantageous in that the strain is conspicuous.
Next, an opposed type roll straightener is shown in FIG. 6. The opposed type roll straightener is disclosed in Japanese Patent Laid-Open Publication No. H08 (1996)-24752 and is provided with, for example, seven upper rolls 71, 72, 73, 74, 75, 76, 77 and seven lower rolls 81, 82, 83, 84, 85, 86, 87, which pairs are each aligned vertically. The seven pairs of upper and lower rolls are disposed in a chevron shape that symmetric about a central pair of upper and lower rolls forming a vertex. This opposed type roll straightener is advantageous in that the strain is less conspicuous, but is disadvantageous in that the roundness is poor.
Thus, the zigzag type and the opposed type each have an advantage and a disadvantage contrary to each other with respect to roundness and strain. Therefore, it has been necessary for a concerned trader to provide two types of machines, i.e., zigzag type and opposed type straighteners, according to the work to be straightened. Consequently, in addition to cost increases, it has been necessary to ensure a correspondingly increased space within the factory concerned.
On the other hand, if all the pairs of upper and lower rolls are made movable vertically and transversely, it may be possible for one roll straightener to serve as both a zigzag type and an opposed type straightener. In such a roll straightener it is not necessary to provide two machines of zigzag type and opposed type, so that the space for a single machine suffices in the factory concerned.
In the roll straightener wherein all the pairs of upper and lower rolls (a total of fourteen rolls) are movable vertically and transversely, the cost can be reduced in comparison with the case where two types of roll straighteners are provided. However, the cost is not reduced much because a lot of means are required for such vertical and transverse movements. Moreover, for switching between the zigzag type and the opposed type, it is necessary to change the positions of the total of fourteen rolls in the vertical and transverse directions. Thus, considerable time is required, and the production efficiency is poor.